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United States Patent |
5,110,378
|
Hasegawa
,   et al.
|
May 5, 1992
|
Metallic glasses having a combination of high permeability, low
coercivity, low ac core loss, low exciting power and high thermal
stability
Abstract
Metallic glasses having high permeability, low coercivity, low ac core
loss, low exciting power, and high thermal stability are disclosed. The
metallic glasses are substantially completely glassy and consist
essentially of about 71 to 79 atom percent iron, about 1 to 6 atom percent
of at least one member selected from the group consisting of chromium,
molybdenum, tungsten, vanadium, niobium, tantalum, titanium, zirconium and
hafnium, about 12 to 24 atom percent boron, about 1 to 8 atom percent
silicon, 0 to about 2 atom percent carbon, plus incidental impurities, the
total of boron, silicon and carbon present ranging from about 18 to 28
atom percent. The alloy is heated treated at a temperature and for a time
sufficient to achieve stress relief without inducing precipitation of
discrete particles therein. Such a metallic glass alloy is especially
suited for use in devices requiring high response to weak magnetic fields,
such as ground fault interruptors and current/potential transformers.
Inventors:
|
Hasegawa; Ryusuke (Morristown, NJ);
Fish; Gordon (Lake Hiawatha, NJ)
|
Assignee:
|
Allied-Signal Inc. (Morris Township, Morris County, NJ)
|
Appl. No.:
|
624485 |
Filed:
|
December 6, 1990 |
Current U.S. Class: |
148/304; 420/64; 420/67; 420/117; 420/121; 420/123 |
Intern'l Class: |
H01F 001/04 |
Field of Search: |
148/307,304,403
420/64,67,117,121,123
|
References Cited
U.S. Patent Documents
Re29989 | May., 1979 | Polk et al. | 148/403.
|
3856513 | Dec., 1974 | Chen et al. | 75/123.
|
4225339 | Sep., 1980 | Inomata et al. | 75/123.
|
4236946 | Dec., 1980 | Aboaf et al. | 148/31.
|
4462826 | Jul., 1984 | Inomata et al. | 75/123.
|
4473413 | Sep., 1984 | Nathasingh et al. | 148/31.
|
Primary Examiner: Sheehan; John P.
Attorney, Agent or Firm: Hampilos; Gus T.
Parent Case Text
This application is continuation of application Ser. No. 235,725 filed on
Aug. 17, 1988 and now abandoned which in turn is a continuation of
application Ser. No. 065,099 filed on Jun. 19, 1987 and now abandoned
which in turn is a continuation of application Ser. No. 825,963 filed Feb.
5, 1986 and now abandoned which in turn is a continuation of application
Ser. No. 594,507 filed on Mar. 29, 1984 and now abandoned which in turn is
continuation-in-part of application Ser. No. 497,391 filed on May 23, 1983
and now abandoned.
Claims
What is claimed is:
1. A metallic alloy having a dc coercivity ranging from about 0.6 to about
4.1 A/m and an ac core loss ranging from about 1.4 to about 5.9 mW/kg, at
60 Hz and 0.1 T, said alloy being substantially completely glassy and
consisting of about 76 and about 78 atom percent iron, about 2 to about 5
atom percent of at least one of chromium and molybdenum, about 14 to about
19 atom percent boron, about 3 to about 6 atom percent silicon, and 0 to
about 1 atom percent carbon, plus impurities, the total of boron, silicon
and carbon present ranging from about 18 to about 22 atom percent.
2. The alloy of claim 1 wherein the alloy has an impedance permeability, at
0.5 T and 60 Hz, of at least about 50,690.
3. The alloy of claim 1, said alloy having been heat treated at a
temperature of about 380.degree.-415.degree. C. for a period of about
0.25-2 hrs. in the presence of a magnetic field.
4. The alloy of claim 1, wherein the total of boron, silicon and carbon
present ranges from about 18 to about 21 atom percent, said alloy having
been heat-treated at a temperature of about 340.degree. to about
415.degree. C. for a period of about 0.25-2 hours.
5. The alloy of claim 1 wherein the composition is Fe.sub.76.75 Cr.sub.2
B.sub.16 Si.sub.5 C.sub.0.25.
6. A metallic alloy having a dc coercivity not exceeding 5.4 A/m and an ac
core loss, at 0.1 T and 60 Hz, not exceeding 4.6 mW/kg said alloy being
substantially completely glassy and having the formula Fe.sub.100-a-b-c
Mo.sub.a B.sub.b Si.sub.c, where the subscripts are in atomic percent, "a"
is from 0.5 to 3, "b" is from 15 to 24, "c" is from 2 to 8 and the sum of
b+c is from 18 to 28.
7. The alloy of claim 6 wherein the ac core loss, at 0.1 T and 60 Hz, is
from 1.6 to 4.6 mW/kg and the dc coercivity is from 1.5 to 5.4 A/m.
8. The alloy of claim 6 wherein the composition to Fe.sub.75 Mo.sub.2
B.sub.15 Si.sub.8.
9. The alloy of claim 6 wherein the composition is Fe.sub.77 Mo.sub.3
B.sub.18 Si.sub.2.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method for enhancing the low frequency magnetic
properties of metallic glasses having high permeability, low
magnetostriction, low coercivity, low ac core loss, low exciting power and
high thermal stability.
2. Description of the Prior Art
As is known, metallic glasses are metastable materials lacking any long
range order. X-ray diffraction scans of glassy metal alloys show only a
diffuse halo similar to that observed for inorganic oxide glasses.
Metallic glasses (amorphous metal alloys) have been disclosed in U.S. Pat.
No. 3,856,513, issued Dec. 24, 1974 to H. S. Chen et al. These alloys
include compositions having the formula M.sub.a Y.sub.b Z.sub.c, where M
is a metal selected from the group consisting of iron, nickel, cobalt,
vanadium and chromium, Y is an element selected from the group consisting
of phosphorus, boron and carbon and Z is an element selected from the
group consisting of aluminum, silicon, tin, germanium, indium, antimony
and beryllium, "a" ranges from about 60 to 90 atom percent, "b" ranges
from about 10 to 30 atom percent and "c" ranges from about 0.1 to 15 atom
percent. Also disclosed are metallic glass wires having the formula
T.sub.i X.sub.j, where T is at least one transition metal and X is an
element selected from the group consisting of phosphorus, boron, carbon,
aluminum, silicon, tin, germanium, indium, beryllium and antimony, "i"
ranges from about 70 to 87 atom percent and "j" ranges from 13 to 30 atom
percent. Such materials are conveniently prepared by rapid quenching from
the melt using processing techniques that are now well-known in the art.
Metallic glasses are also disclosed in U.S. Pat. No. 4,067,732 issued Jan.
10, 1978. These glassy alloys include compositions having the formula
M.sub.a M'.sub.b Cr.sub.c M".sub.d B.sub.e, where M is one iron group
element (iron, cobalt and nickel), M' is at least one of the two remaining
iron group elements, M" is at least one element of vanadium, manganese,
molybdenum, tungsten, niobium and tantalum, B is boron, "a" ranges from
about 40 to 85 atom percent, "b" ranges from 0 to about 45 atom percent,
"c" and "d" both range from 0 to 20 atom percent and "e" ranges from about
15 to 25 atom percent and "e" ranges from about 15 to 25 atom percent,
with the provision that "b", "c" and "d" cannot be zero simultaneously.
Such glassy alloys are disclosed as having an unexpected combination of
improved ultimate tensile strength, improved hardness and improved thermal
stability.
These disclosures also mention unusual or unique magnetic properties for
many metallic glasses which fall within the scope of the broad claims.
However, metallic glasses possessing a combination of higher permeability,
lower magnetostriction, lower coercivity, lower core loss, lower exciting
power and higher thermal stability than prior art metallic glasses are
required for specific applications such as ground fault interrupters,
relay cores, transformers and the like.
SUMMARY OF THE INVENTION
The present invention provides a method of enhancing the magnetic
properties of a metallic glass alloy having a combination of high
permeability, low magnetostriction, low coercivity, low ac core loss, low
exciting power and high thermal stability. The metallic glasses consist
essentially of about 71 to 79 atom percent iron, about 0.5 to 6 atom
percent of at least one member selected from the group consisting of
chromium, molybdenum, tungsten, vanadium, niobium/ tantalum, titanium,
zirconium, and hafnium, about 12 to 24 atom percent boron, about 1 to 8
atom percent silicon, 0 to about 2 atom percent carbon, plus incidental
impurities, the total of boron, silicon, and carbon present ranging from
about 18 to 28 atom percent. The method comprises the step of
heat-treating the metallic glass alloy for a time and at a temperature
sufficient to achieve stress relief without inducing precipitation of
discrete particles therein and at least cooling the alloy in the presence
of an applied magnetic field.
Metallic glass alloys treated in accordance with the method of this
invention are especially suitable for use in devices requiring high
response to weak magnetic fields, such as ground fault interrupters and
current/potential transformers.
DETAILED DESCRIPTION OF THE INVENTION
Heat treatment of the metallic glass alloys of the invention enhances the
magnetic properties thereof. More specifically, upon heat treatment in
accordance with the invention, the metallic glass alloys evidence a
superior combination of the following thermal and magnetic properties: (i)
high maximum permeability (e.g. a maximum of about 250,000-300,000 at 60
Hz), low magnetostriction (about 12-24 ppm), low coercivity (about 0.25-2
A/m), low ac core loss (about 1.5-3 mW/kg at 60 Hz and 0.1 T), low
exciting power (1.7-5 mVA/kg) and high thermal stability (fist
crystallization temperature of about 475.degree.-600.degree. C.). The
alloys consist essentially of about 71 to 79 atom percent iron, about 0.5
to 6 atom percent of at least one member selected from the group
consisting of chromium, molybdenum, tungsten, vanadium, niobium, tantalum,
titanium, zirconium, and hafnium, about 12 to 24 atom percent boron, about
1 to 8 atom percent silicon, 0 to about 2 atom percent carbon, plus
incidental impurities, the total of boron, silicon, and carbon present
ranging from about 18 to 28 atom percent. The alloys of the present
invention are substantially completely glassy, that is to say, they are at
least about 95% amorphous, preferably at least about 97% amorphous, and,
most preferably, 100% amorphous as determined by transmission electron
microscopy and X-ray diffraction. The best magnetic properties are
obtained in alloys having the greatest volume percent of amorphous
material. The heat-treating step comprises the steps of (a) heating the
alloy to a temperature at least that sufficient to achieve stress relief
without inducing precipitation of discrete particles therein; (b) cooling
the alloy to a temperature below about 200.degree. C.; and (c) applying a
magnetic field to the alloy during at least the cooling step. The cooling
step is typically carried out at a cooling rate of about -0.5.degree.
C./min to -100.degree. C./min and preferably at a rate of about
-0.5.degree. C./min to -20.degree. C./min. However, faster cooling rates
of at least about -1000.degree. C./min, such as are achieved by quenching
the alloy in a liquid medium selected from the group consisting of water,
brine and oil, can also be used. The highest permeability is obtained in
an alloy which is cooled slowly, for example, at a rate of between about
-0.5.degree. C./min and -10.degree. C./min.
A heat treatment carried out in the absence of an applied magnetic field
results in insufficient improvement of the properties of permeability,
core loss and coercivity.
It is generally found that the process of forming metallic glass alloys
results in cast-in stresses. Further stresses may be introduced by the
process of fabricating cores from metallic glass alloys. Hence it is
preferred that the metallic glass alloy be heated to a temperature and
held for a time sufficient to relieve these stresses. Furthermore, during
that heat treatment, the presence of a magnetic field enhances the
formation of magnetic anisotropy in the direction along which the field is
applied. The field is especially effective when the alloy is at a
temperature which is near the Curie temperature or up to 50.degree. C.
below and which is high enough to allow atomic diffusion or rearrangement.
Thus it is especially preferred that the alloy be annealed at a
temperature above the Curie temperature and that it be cooled through the
Curie temperature and to a temperature at least 50.degree. C. therebelow
in the presence of applied field. Below about 200.degree. C., the atomic
mobility is too low for the field to be of particular effectiveness.
The resulting material is especially suited for application in magnetic
devices operating at line frequencies (50-400 Hz).
The magnetic cores of the invention are preferably fabricated by first
forming the metallic glass into the desired final shape (e.g., a core) and
then subjecting the core to the appropriate heat treatment described
herein. The magnetic fields are applied in the longitudinal or transverse
directions, defined, respectively, as the direction along which the core
is magnetically excited during operation and the direction perpendicular
to that of magnetic excitation during operation. Most preferably, the core
is a wound toroid in which a continuous ribbon of metallic glass is wound
upon itself or upon a supporting bobbin. For such a core, the longitudinal
direction is the circumferential direction in which the ribbon is wound
and the transverse direction is parallel to the axis of the toroid. A
longitudinal magnetic field (H.parallel.) is conveniently applied to a
toroid either by passing a suitable electric current through a set of
toroidally wound windings or by passing a suitable current through at
least one conductor directed through the center of, and parallel to the
axis of, the toroid. A transverse magnetic field (H.perp.) is conveniently
applied by placing the toroid coaxially between the poles either of
permanent magnets or of an electromagnet or by placing the toroid
coaxially inside a solenoid energized by a suitable electric current.
The temperature (T.sub.a) and holding time (t.sub.a) of the preferred heat
treatment of the metallic glasses of the present invention are dependent
on the composition of the alloy. When the total of boron, silicon and
carbon present is about 18-21 atom percent and the total of the elements
of the groups IVA, VA, and VIA (i.e., Mo, Cr, Ti, Ta, W, Hf, Zr, Nb, and
V) present is about 1-2 atom percent, then T.sub.a is about
340.degree.-400.degree. C. and t.sub.a is 0.25-1 h; when the total of
boron, silicon, and carbon present is about 18-21 atom percent and the
total of the elements of groups IVA, VA, and VIA present is about 3-6 atom
percent, then T.sub.a is about 340.degree.-415.degree. C. and T.sub.a is
0.25-2 h; when the total of boron, silicon, and carbon present is about
22-28, then T.sub.a is about 340.degree.-415.degree. C. ant t.sub.a is
0.25-2 h.
The method of enhancing the magnetic properties of the alloys of the
present invention is further characterized by the choice of two different
directions of the magnetic field applied during the heat treatment. The
direction is chosen on the basis of the desired final properties.
The first preferred method comprises a heat treatment in a longitudinal
field whose preferred strength ranges from about 200 to 4000 A/m. The
temperature and duration of anneal are chosen to be adequate to achieve
stress relief without inducing precipitation of discrete particles in the
alloy. The resulting material is characterized by a square hysteresis loop
with low coercivity and high permeability, especially for excitation at
frequencies of 50-400 Hz. Preferably, the squareness ratio, defined as the
ratio of remanent to saturation induction, is at least 0.90, the maximum
permeability measured at 60 Hz is at least 250,000, and more preferably,
at least 300,000, and the coercivity is less than 1 A/m, preferably less
than 0.75 A/m, and most preferably less than 0.5 A/m. Magnetic cores
fabricated with such annealed material are especially suited for devices
such as ground fault interrupters which detect the presence of low ac
magnetic fields. The high magnetic permeability renders such devices more
sensitive.
The second preferred method is a heat treatment in the presence of a
transverse field, and, optionally, in the presence of a mixed magnetic
field having a first component applied in the transverse direction and a
second component applied in the longitudinal direction. For heat treatment
in the presence of a transverse field, the field strength is typically
about 2400 to 16,000 A/m. For heat treatment in the presence of a mixed
field, the first component has a strength of about 4,000 to 16,000 A/m and
the second component has a strength of about 0 to about 2400 A/m. The
duration and temperature of heat treatment are chosen as in the first
method. The resulting material is characterized by low dc coercivity, low
squareness ratio, and high permeability over a wide range of applied
field, Preferably, the coercivity is less than 0.75 A/m and, within a
range of magnetic fields applied at 60 Hz whose maximum and minimum peak
amplitudes are in a ratio of at least 25:1, the impedance permeability is
at least 40,000 and varies by no more than a factor of three. That is, the
maximum and minimum values of the impedance permeability have a ratio not
exceeding about 3:1. Magnetic cores fabricated with such annealed material
are especially suited for applications such as current/potential
transformers which measure the intensity of an ac field. The near constant
permeability allows a device such as a current/potential transformer to
provide a linear output over a wide range of applied fields. The high
permeability renders a device more sensitive at lower applied fields.
Alloys heat-treated with applied transverse field in accordance with
present invention have a further advantage in their higher permeability
under unipolar magnetic excitation than that of heat-treated alloys of the
prior art. The magnetic permeability measured under unipolar excitation
(e.g., full-wave or half-wave rectified ac current) is generally much
lower than that measured under bipolar excitation (e.g., sinusoidal
current), since the maximum unipolar flux swing is limited to the
difference between saturation and remanent induction measured at the
desired frequency, compared to twice the saturation induction for bipolar
excitation. Furthermore, the BH loop of prior art materials has higher
squareness ratio when measured at line frequencies than at dc, leading to
a further reduction in the difference between saturation and remanence
and, hence, lower unipolar permeability. In contrast, the heat-treated
alloys of the present invention show acceptably high unipolar flux swing
and permeability. For example, Table I compares permeabilities of
Fe.sub.76.5 Cr.sub.2 B.sub.16 Si.sub.5 C.sub.0.25 annealed with the method
of present invention and Fe.sub.78 B.sub.13 Si.sub.9 annealed by the prior
art method, demonstrating the superiority of the present invention.
TABLE I
______________________________________
Permeabilities of (A) Fe.sub.76.5 Cr.sub.2 B.sub.16 Si.sub.5 C.sub.0.25
metallic
glass annealed at 400.degree. C. for 1 h with H.parallel. = 1600 A/m and
H.perp. = 8000 A/m and (B) prior art Fe.sub.78 B.sub.13 Si.sub.9 annealed
with
H.parallel. = 800 A/m at 400.degree. C. for 2 h and excited with
sinusoidal
(bipolar) and full-wave rectified sinusoidal (unipolar)
60 Hz current to the maximum field H.sub.m shown.
Impedance Permeability
H.sub.m (A/m) A B
______________________________________
(Unipolar)
0.16 27,000 4,645
0.40 45,370 2,312
0.80 71,900 2,934
1.60 106,020 6,868
2.40 106,550 8,282
2.80 -- 7,544
3.20 106,060 --
3.60 -- 7,182
4.00 101,420 --
4.80 92,324 6,290
(Bipolar)
0.16 19,090 1,295
0.40 66,070 3,077
0.80 107,670 19,040
1.60 129,712 66,410
2.40 126,670 157,490
3.20 117,890 167,370
4.00 109,490 143,360
4.80 102,230 121,840
______________________________________
Metallic glass alloys consisting essentially of about 68 to 78 atom percent
iron, about 2 to 5 of at least one number selected from the group
consisting of chromium and molybdenum, about 14 to 19 atom percent boron,
about 3 to 6 atom percent silicon, from 0 to 1 atom percent carbon, the
total of boron, silicon and carbon present ranging from about 18 to 22,
when heat treated at a temperature of 380.degree.-415.degree. C. for a
period of 0.25-2 hours in the presence of an applied magnetic field,
produce a particularly outstanding combination of high permeability, low
coercivity, low ac core loss, low exciting power and high thermal
stability. These properties make the alloys especially suited for use in
ground fault interrupters and current/potential transformers. Accordingly
such alloys are preferred.
Saturation magnetostriction is the change in the length of a magnetic
material under the influence of a saturating magnetic field. A lower
saturation magnetostriction renders a material less sensitive to
externally applied stresses. Magnetostriction is usually discussed in
terms of the ratio of the change in length to the original length, and is
given in parts per million (ppm). Prior art iron rich metallic glasses
evidence saturation magnetostrictions of about 30 ppm as do metallic
glasses without the presence of any of the elements belonging to the IVA,
VA, and VIA columns of the periodic table, such as molybdenum. For
example, a prior art iron rich metallic glass designated for use in line
frequency applications and having the composition Fe.sub.78 B.sub.13
Si.sub.9 has a saturation magnetostriction of about 30 ppm. In contrast, a
metallic glass of the invention having the composition Fe.sub.76.75
Cr.sub.2 B.sub.16 Si.sub.5 C.sub.0.25 has a saturation magnetostriction of
about 20 ppm.
It is well-known as a guiding principle in the art of magnetic materials
that reduction of magnetostriction by appropriate selection of alloy
composition yields a product with enhanced magnetic properties, such as
higher permeability and reduced core loss. See, e.g., Richard M. Bozorth,
Ferromagnetism (New York: D. Van Nostrand, 1951), pp. 626-627. The alloys
of the present invention have magnetic properties for line frequency
(50-400 Hz) applications that are far better than would be expected, given
that their saturation magnetostrictions (.lambda..sub.s) are in the range
of 18-22 ppm. Their line frequency properties are comparable to those of
the FeNi-based glasses containing nearly equal amounts of Fe and Ni
(.lambda..sub.2=.sup..congruent. 8-12 ppm) and crystalline permalloys
containing about 80 percent Ni (.lambda..sub.s=.sup..congruent. 0)
The prior art FeNi- and Co-based amorphous alloys and crystalline
permalloys require the presence of a substantial fraction of either Ni or
Co to achieve the desired properties. The relatively higher raw material
cost of Ni and Co compared to that of Fe therefore renders these prior art
amorphous and crystalline alloys inferior for application to the
heat-treated alloys of the present invention.
Ac core loss is that energy loss dissipated as heat. It is the hysteresis
in an ac field and is measured by the area of a B-H loop for low
frequencies (less than about 1 kHz) and from the complex input power in
the exciting coil for high frequencies (about 1 kHz to 1 MHz). The major
portion of the ac core loss at high frequencies arises from the eddy
current generated during flux change. However, a smaller hysteresis loss
and hence a smaller coercivity is desirable especially at line frequency.
A lower core loss renders a material more useful in certain applications
such as tape recorder heads and transformers. Core loss is discussed in
units of watts/kg at a specified maximum induction level and at a
specified frequency. For example, a prior art heat-treated metallic glass
having the composition Fe.sub.40 Ni.sub.36 Mo.sub.4 B.sub.20 has an ac
core loss of 0.07 watts/kg at an induction of 0.1 Tesla and a frequency of
1 kHz, while a metallic glass having the composition Fe.sub.76 Mo.sub.4
B.sub.20 has an ac core loss of 0.08 watts/kg at an induction of 0.1 Tesla
and the same frequency. In contrast, a metallic glass alloy of the
invention having the composition Fe.sub.76.75 Cr.sub.2 B.sub.16 Si.sub.5
Co.sub.0.25 has an ac core loss of 0.06 watts/kg at an induction of 0.1
Tesla and the same frequency.
Exciting power is a measure of power required to maintain a certain flux
density in a magnetic material. It is desirable that a magnetic material
to be used in magnetic devices have an exciting power as low as possible.
Exciting power (P.sub.e) is related to the above-mentioned core loss (L)
through the relationship L=P.sub.e sin .delta. where .delta. is the phase
shift between the exciting field and the resultant induction. The phase
shift is also related to the magnetostriction in such a way that a lower
magnetostriction value leads to a lower phase shift. It is then
advantageous to have the magnetostriction value as low as possible. As
mentioned earlier, prior art iron-rich metallic glasses such as Fe.sub.78
B.sub.13 Si.sub.9 have the magnetostriction value near 30 ppm, in contrast
to the magnetostriction value of about 20 ppm of the metallic glasses of
the present invention.
Magnetic permeability is the ratio of induction to applied magnetic field.
A higher permeability renders a material more useful in certain
applications such as ground fault interrupters, due to the increased
sensitivity. A particular measure of permeability under ac excitation is
impedance permeability, defined to be the ratio of the apparent maximum
induction to the apparent maximum magnetic field, as determined for a
magnetic core from the root mean square (rms) value of the voltage induced
in a set of secondary windings and the rms value of exciting current in a
set of primary windings, respectively. Especially noted is the fact that a
heat-treated Fe.sub.76.75 Cr.sub.2 B.sub.16 Si.sub.5 C.sub.0.25 metallic
glass has an impedance permeability of about 300,000 while the best
heat-treated prior art Fe.sub.78 B.sub.13 Si.sub.9 metallic glass has an
impedance permeability of 100,000 at 60 Hz and at the induction level of
0.6 Tesla.
In applicant's application Ser. No. 497,391 filed May 23, 1983, it is
disclosed and claimed that the high frequency (f>1 kHz) magnetic
properties of certain iron-based metallic glasses are enhanced by a heat
treatment at a temperature and for a time sufficient to induce
precipitation of discrete particles into the amorphous matrix. Such a heat
treatment is distinguished from the heat treatment of the present
invention in that the line frequency properties of metallic glasses heat
treated according to the method of the present invention are superior to
those of glasses heat treated according to the method of the prior
inventions. Conversely, the high frequency properties of metallic glasses
heat-treated according to the method of the prior invention are superior.
Table II shows representative properties of a metallic glass having the
composition Fe.sub.76.75 Cr.sub.2 B.sub.16 Si.sub.5 C.sub.0.25
heat-treated according to the methods of the present and the prior
inventions.
TABLE II
__________________________________________________________________________
Magnetic properties of toroids fabricated with
Fe.sub.76.75 Cr.sub.2 B.sub.16 Si.sub.5 C.sub.0.25 metallic glass and
heat-treated by
the method of the present invention (A) and by the
method of Application Serial Number 497,391 (B). Sample
A was treated at 400.degree. C. for 1 h in the presence of an
800 A/m longitudinal field. Sample B was treated at
440.degree. C. for 2.0 h in the same field. Core loss (L),
exciting power (P.sub.e) and impedance permeability .mu..sub.z were
measured at f = 60 Hz/B.sub.m = 0.1 Tesla and at f = 50k Hz/Bm = 0.1
Tesla.
H.sub.c
60 Hz properties 50k Hz properties
(A/m) L (mW/kg)
P.sub.e (mVA/kg)
.mu..sub.z
L (W/kg)
P.sub.e (VA/kg)
.mu..sub.z
__________________________________________________________________________
A.
0.87
2.4 2.5 86,860
66.6 72.8 2365
B.
4.9 2.8 5.9 37,120
27.0 39.0 4415
__________________________________________________________________________
As is well known in the art (see, e.g., Donald G. Fink and H. Wayne Beaty,
Standard Handbook for Electrical Engineers (New York: McGraw Hill, 1978)
pp 3-23-3-24), current/potential transformers are devices used to monitor
currents or voltages either where the currents or voltages are too large
for conventional meters or where it is desired to have the measuring
instrument electrically isolated from the circuit being tested. The
transformer typically comprises a toroidal core with primary and secondary
windings.
For monitoring current, the primary consists of at most a few turns
connected in series with the load and the secondary has many turns,
frequently more than 200. For monitoring potential, the primary has many
turns and is connected in parallel with the load and the secondary has few
turns. The voltage induced in the secondary is proportional to the primary
current or voltage, as appropriate.
It has long been recognized in the art (see, e.g., H. Pender, W. A. Del
Mar, and K. McIlwain, Electrical Engineers' Handbook: Electrical Power
(New York: John Wiley, 1941), pp. 5-55-5-60.) that smaller, more
efficient, and more accurate current/potential transformers could be built
by employing magnetic cores having higher permeability, lower losses,
lower phase shift and lower exciting power. Yet up to the time of the
present invention, metallic glass cores having the requisite combination
of properties, e.g. high maximum permeability, low magnetostriction, low
ac core loss, low exciting power and high thermal stability, have not been
available. It has been discovered that cores comprised of metallic glass
alloys annealed in accordance with the present invention have this
requisite combination of properties. Hence, current/potential transformers
employing the magnetic cores of the invention are superior to transformers
employing prior art cores.
As is well known in the art, e.g., U.S. Pat. No. 4,363,103 issued Oct. 5,
1982 to G. A. Whitlow, a ground fault interrupter is an electrical
protective device which interrupts the flow of electrical supply current
to a circuit upon occurrence of a ground fault, i.e., an imbalance between
the current flowing from the electrical power distribution system into a
load and the current returning to the distribution system from the other
side of the load. Such an imbalance is indicative of a ground fault
current flowing from some point in the load to ground by an alternate
path. Such a leakage current is potentially hazardous, as in the case of a
leakage current flowing through the body of the user of a defective
appliance. Ground fault interruption means are now required by electrical
codes for electrical service in certain hazardous locations, e.g., outlets
in garages, bathroom, and outdoors.
A ground fault interrupter frequently comprises a differential current
transformer with a toroidal magnetic core. The primary of the transformer
has separate windings through which the supply current and the return
current, respectively, pass. The windings are disposed in such a manner
that when the supply and return currents are equal, i.e., no ground fault
exists, the magnetic fields produced by the separate windings cancel. When
a ground fault occurs, the cancellation is no longer exact. The resulting
ac magnetic field induces a voltage in a multiturn secondary winding which
is used to activate means for interrupting the flow of supply current.
The sensitivity of a ground fault interrupter is determined by the
permeability of the magnetic core. That is, for a given size of core, the
ground fault current trip level decreases as permeability increases.
Alternatively, the core size needed for a ground fault interrupter
designed to trip at a given ground fault current decreases as the
permeability of the core increases. Hence, the high permeability alloys of
the present invention are highly preferred for application in ground fault
interrupters. Devices comprising differential current transformers with
the toroidal magnetic cores of the invention have lower ground fault
current trip levels and/or smaller size than devices employing prior art
cores.
EXAMPLES
Example 1
Fe-Mo-B-Si
Ribbons having compositions given by Fe.sub.100-a-b-c-a Mo.sub.a B.sub.b
Si.sub.c and having dimensions about 0.5 to 1 cm wide and about 25 to 50
.mu.m thick were formed by squirting a melt of the particular composition
through an orifice by an overpressure of argon onto a rapidly rotating
copper chill wheel (surface speed about 3000 to 6000 ft/min.). Magnetic
cores were formed by winding the ribbon thus produced onto toroidal
ceramic bobbins and were heat-treated in a tube furnace. Longitudinal
magnetic fields were produced by passing the requisite electric current
through a set of copper windings applied to the toroid. Transverse
magnetic fields were produced either by placing the toroids axially
between the poles of two permanent magnets or by placing the toroid
coaxially within a solenoid carrying the requisite electric current.
Impedance permeability, magnetostriction, core loss, magnetization and
coercive field were measured by conventional techniques employing B-H
loops, metallic strain gauges and vibrating sample magnetometer. Curie
temperature and crystallization temperature were measured, respectively,
by an induction method and by differential scanning calorimetry. The
measured values of room temperature saturation induction, Curie
temperature, room temperature saturation magnetostriction and the first
crystallization temperature are summarized in Table III below.
TABLE III
______________________________________
Examples of basic physical and magnetic properties
of Fe--Mo--B--Si amorphous alloys. .theta..sub.f and T.sub.x1 are ferro-
magnetic Curie and first crystallization temperatures,
respectively. B.sub.s and .lambda..sub.s are the room temperature satu-
ration induction and saturation magnetostriction,
respectively. .rho. is the mass density.
Composition (at. %)
.theta..sub.f
B.sub.s
.rho. .lambda.
T.sub.x1
Fe Mo B Si (.degree.C.)
(T) (g/cm.sup.3)
(10.sup.-6)
(.degree.C.)
______________________________________
79 2 17 2 299 1.35 7.47 21.9 509
79 2 15 4 318 1.42 7.43 24.3 517
79 2 13 6 300 1.36 7.39 24.4 511
77 2 19 2 319 1.41 7.47 22.6 522
77 2 17 4 352 1.41 7.43 25.4 532
77 2 15 6 335 1.38 7.37 26.2 548
75 2 21 2 357 1.39 7.48 21.4 538
75 2 19 4 352 1.36 7.37 21.7 552
75 2 17 6 355 1.38 7.48 22.9 561
78 3 17 2 256 1.30 7.61 19.0 520
78 3 15 4 282 1.35 7.51 21.3 524
78 3 13 6 258 1.27 7.43 18.9 519
76 3 19 2 283 1.26 7.42 18.2 534
76 3 17 4 318 1.34 7.37 22.7 539
76 3 15 6 287 1.29 7.40 21.4 552
74 3 21 2 326 1.29 7.45 19.3 550
74 3 19 4 312 1.28 7.40 19.1 560
74 3 17 6 314 1.28 -- 19.3 565
71 1 24 4 433 1.42 -- 21.3 561
72 6 18 4 234 1.07 7.46 13.0 569
72 4 20 4 400 1.41 -- 25.1 563
74 2 20 4 370 1.33 7.40 23.3 601
73 3 20 4 379 1.33 -- 20.6 541
77 2 13 8 328 1.34 -- 21.8 545
75 2 15 8 353 1.41 -- 23.7 574
71 3 20 6 372 1.38 -- 20.0 583
71 3 18 8 421 1.44 -- 17.8 579
77.5 1.5 16 5 359 1.45 -- 26.6 536
77 2 20 1 329 1.40 -- 23.20 518
78.5 0.5 16 5 395 1.46 -- 24.4 525
______________________________________
The magnetic properties of these glassy alloys after annealing in a
longitudinal applied field are presented in Table IV.
The presence of molybdenum is seen to increase the permeability and the
crystallization temperature and to lower the ac core loss, exciting power
and magnetostriction. The combination of these properties make these
compositions suitable for line frequency devices such as ground fault
interrupters and current transformers.
TABLE IV
__________________________________________________________________________
Examples of 60 Hz magnetic properties of
Fe.sub.100-a-b-c Mo.sub.a B.sub.b Si.sub.c metallic glasses. Samples
were
heat-treated at a temperature T.sub.a for a holding time
t.sub.a = 1 h in the presence of an 800 A/m longitudinal
field. Values of the dc remanent induction B.sub.r, dc
coercivity, H.sub.c, and 60 Hz impedance permeability .mu..sub.z at
maximum induction B.sub.m = 0.1 and 0.5 Tesla are shown.
Composition (at. %) L (mW/kg,
.mu..sub.z
Fe Mo B Si
T.sub.a (.degree.C.)
H.sub.c (A/m)
B.sub.r (T)
B.sub.m = 0.1 T)
0.1 T
0.5 T
__________________________________________________________________________
77 3 18
2 380 1.7 0.77
2.5 67,190
174,480
78 2 18
2 380 2.5 1.05
4.0 45,020
129,300
77 3 16
4 400 2.7 0.59
2.6 43,340
81,410
79 2 17
2 380 2.7 0.74
2.9 43,680
100,090
79 2 15
4 380 2.0 1.01
3.0 56,080
151,490
79 2 13
6 380 2.2 0.79
3.4 50,110
120,800
77 2 19
2 380 1.8 0.78
3.2 54,830
126,150
77 2 17
4 400 2.8 0.90
3.7 42,050
113,410
77 2 15
6 400 3.8 0.56
2.7 37,170
51,714
75 2 21
2 400 2.4 0.79
3.8 45,990
101,060
75 2 19
4 400 3.9 0.58
2.9 31,230
51,160
75 2 17
6 400 5.4 0.40
3.6 24,280
31,720
78 3 17
2 400 3.6 0.20
1.6 17,440
14,812
78 3 15
4 400 3.6 0.54
2.4 37,200
50,690
78 3 13
6 400 2.0 0.73
2.7 54,740
134,370
76 3 19
2 400 2.2 0.51
2.6 51,160
60,430
76 3 17
4 380 3.4 0.76
3.7 36,250
90,930
74 3 21
2 400 3.2 0.55
3.1 39,740
49,750
74 3 19
4 400 2.9 0.52
3.2 40,600
106,380
74 3 17
6 400 1.7 0.67
2.6 61,170
114,300
71 1 24
4 400 2.5 0.84
4.2 44,870
129,274
78.5
0.5
16
5 400 2.2 1.22
4.6 44,420
139,660
75 2 15
8 400 1.5 0.74
2.0 79,570
177,620
__________________________________________________________________________
Example 2
Fe-Cr-B-Si System
Ribbons having compositions given by Fe.sub.100-a-b-c Cr.sub.a -B.sub.b
-Si.sub.c and having dimensions about 0.5-1 cm wide and about 25 to 50
.mu.m thick were formed as in Example 1.
The magnetic and thermal data are summarized in Table V below. The magnetic
properties of these glassy alloys after annealing are presented in Table
VI.
The line frequency magnetic properties of these metallic glasses are
comparable to those containing molybdenum (Example 1).
A combination of low ac core loss and high impedance permeability at line
frequency is achieved in the metallic glasses of the present invention.
The thermal stability is also shown to be excellent as evidenced by high
crystallization temperature. These improved combination of properties of
the metallic glasses of the present invention renders these compositions
suitable for line frequency magnetic devices such as ground fault
interrupters, current/potential transformers and the like.
TABLE V
______________________________________
Examples of basic physical and magnetic properties
of Fe--Cr--B--Si amorphous alloys. .theta..sub.f and T.sub.x1 are the
fer-
romagnetic Curie and first crystallization temperatures,
respectively. B.sub.s and .lambda..sub.s are the room temperature satu-
ration induction and saturation magnetostriction,
respectively. .rho. is the mass density.
Composition (at. %)
.theta..sub.f
B.sub.s
.rho. .lambda..sub.s
T.sub.x1
Fe Cr B Si (.degree.C.)
(T) (g/cm.sup.3)
(10.sup.-6)
(.degree.C.)
______________________________________
71 1 24 4 444 1.41 -- 15.8 537
79 2 17 2 309 1.44 7.46 23.8 494
79 2 15 4 315 1.44 -- 26.6 503
77 2 19 2 341 1.42 -- 24.5 499
77 2 17 4 344 1.43 7.33 26.4 514
75 2 21 2 371 1.42 -- 14.5 506
75 2 19 4 372 1.40 7.36 21.4 534
78 3 17 2 283 1.33 7.37 19.8 496
78 3 13 6 297 1.32 7.30 20.3 497
78 3 15 4 289 1.33 -- 20.9 504
76 3 19 2 314 1.35 -- 22.2 500
76 3 17 4 315 1.33 7.40 20.0 518
74 3 21 2 343 1.32 7.25 23.0 506
74 3 19 4 342 1.32 -- 22.4 538
72 6 18 4 251 1.09 -- 11.1 534
72 4 20 4 313 1.24 -- 12.2 599
74 2 20 4 386 1.40 -- 11.1 545
73 3 20 4 362 1.33 -- 17.9 547
77 2 13 8 400 1.52 -- 32.6 531
71 3 20 6 355 1.27 -- 20.3 552
71 3 18 8 367 1.31 7.09 18.6 568
75 2 15 8 368 1.40 7.58 15.4 553
77.5 1.5 16 5 360 1.48 -- 28.8 520
77 2 15.8 5.2 360 1.40 -- 24.0 523
75 2 17.8 5.2 369 1.40 -- 26.6 536
76 3 15.8 5.2 323 1.33 7.23 23.5 526
74 3 17.8 5.2 346 1.30 -- 23.4 541
78.5 0.5 16 5 395 1.35 -- 24.9 520
______________________________________
TABLE VI
__________________________________________________________________________
Examples of 60 Hz magnetic properties of
Fe.sub.100-a-b- Cr.sub.a B.sub.b Si.sub.c metallic glasses. Samples were
heat-
treated at a temperature T.sub.a for a holding time t.sub.a = 1 h in
the presence of an 800 A/m longitudinal field. Values
of the dc remanent induction B.sub.r, dc coercivity H.sub.c, and
60 Hz impedance permeability .mu..sub.z at maximum inductions of
0.1 and 0.5 Tesla are shown.
Composition (at. %) L (mW/kg,
.mu..sub.z
Fe Cr B Si
T.sub.a (.degree.C.)
H.sub.c (A/m)
B.sub.r (T)
B/.sub.m = 0.1 T)
B/.sub.m = 0.1 T
0.5 T
__________________________________________________________________________
79 2 17
2 380 3.2 0.81
5.4 30,848 89,720
79 2 15
2 380 3.4 1.14
5.5 35,220 86,090
79 2 13
6 380 2.5 1.06
5.1 37,000 115,970
77 2 19
2 380 2.1 1.02
3.7 47,990 144,810
77 2 17
2 400 1.5 0.94
2.9 66,000 165,080
77 2 15
6 400 2.7 0.98
4.1 41,890 120,860
75 2 21
2 400 1.5 0.90
2.6 69,380 166,420
75 2 17
6 400 1.1 0.90
2.3 83,120 192,870
78 3 17
2 400 3.6 0.91
5.5 28,870 95,530
78 3 15
4 400 4.1 0.95
5.9 27,740 90,011
78 3 13
6 400 3.1 1.07
5.0 34,580 113,040
76 3 19
2 400 1.8 0.92
3.6 52,150 149,310
76 3 17
4 400 1.7 1.08
3.3 59,480 160,100
76 3 15
6 400 2.1 0.87
4.0 46,680 126,590
74 3 21
2 400 2.1 0.87
3.6 47,350 129,440
74 3 19
4 400 1.1 0.85
2.3 81,010 190,312
74 3 17
6 400 1.5 0.89
3.0 61,550 154,080
78.5
0.5
16
5 400 1.7 1.02
3.2 61,540 172,910
__________________________________________________________________________
Example 3
Fe-M-B-Si System
Ribbons having composition given by Fe.sub.100-a-b-c M.sub.a -B.sub.b
-Si.sub.c, where M is at least one of tungsten, vanadium, niobium,
tantalum, titanium, zirconium, and hafnium, and having dimensions about
0.5-1 cm wide and about 25 to 50 .mu.m thick were formed as in Example 1.
The magnetic and thermal data are summarized in Table VII below. The
magnetic properties of these glassy alloys after annealing are presented
in Table VIII.
The line frequency magnetic properties of these metallic glasses are
comparable to those containing molybdenum (Example 1).
A composition of low ac core loss and high impedance permeability at line
frequency is achieved in the metallic glasses of the present invention.
The thermal stability is also shown to be excellent as evidenced by high
crystallization temperature. The improved combination of properties of the
metallic glasses of the present invention renders these compositions
suitable for line frequency magnetic devices such as ground fault
interrupters, current/potential transformers and the like.
TABLE VII
______________________________________
Examples of basic physical and magnetic properties
of Fe--M--B--Si amorphous alloys, where M.dbd.Nb, V, W, Zr, Ti,
Hf, or Ta. .theta..sub.f and T.sub.x1 are the ferromagnetic and first
crystallization temperatures, respectively, B.sub.s and .lambda..sub.s
are the room temperature saturation induction and satu-
ration magnetostriction, respectively, .rho. is the mass
density.
T.sub.x1
Composition
.theta..sub.f (.degree.C.)
B.sub.s (T)
.rho. (g/cm.sup.3)
.lambda. (10.sup.-6)
(.degree.C.)
______________________________________
Fe.sub.73 Nb.sub.3 B.sub.20 Si.sub.4
320 1.25 7.37 17.4 586
Fe.sub.73 V.sub.3 B.sub.20 Si.sub.4
350 1.34 -- 20.1 560
Fe.sub.78.5 W.sub.1.5 B.sub.17 Si.sub.3
345 1.39 -- 22.0 521
Fe.sub.78.5 Zr.sub.1.5 B.sub.17 Si.sub.3
356 1.52 7.44 26.1 533
Fe.sub.78.5 Ti.sub.1.5 B.sub.17 Si.sub.3
355 1.42 -- 29.3 524
Fe.sub.73 Ti.sub.3 B.sub.20 Si.sub.4
381 1.48 -- 25.6 535
Fe.sub.78.5 Hf.sub.1.5 B.sub.17 Si.sub.3
355 1.37 -- 24.8 543
Fe.sub.78.5 Ti.sub.1.5 B.sub.17 Si.sub.3
355 1.42 -- 29.3 524
Fe.sub.73 Hf.sub.3 B.sub.20 Si.sub.4
354 1.28 -- 19.3 587
Fe.sub.73 Ta.sub.3 B.sub.20 Si.sub.4
406 1.39 -- 15.4 571
______________________________________
TABLE VIII
__________________________________________________________________________
Examples of the 60 Hz magnetic properties of Fe.sub.100-
.sub.a-b-c --M.sub.a --B.sub.b --Si.sub.c metallic glasses listed in
Table VII.
Samples were heat-treated at temperature T.sub.a for a hold-
ing time t.sub.a in the presence of a longitudinal annealing
field H.parallel.. Values of the dc coercive field H.sub.c and
remanent inductions B.sub.r and 60 Hz properties of impedance
permeability .mu..sub.z and core loss L at specified maximum
induction level B.sub.m are given.
T.sub.a
t.sub.a
H.parallel.
B.sub.r
H.sub.c
L (mW/kg,
.mu..sub.z
Composition
(.degree.C.)
(h)
(A/m)
(T)
(A/m)
B.sub.m = 0.1 T)
0.1 T
0.5 T
__________________________________________________________________________
Fe.sub.78.5 Hf.sub.1.5 B.sub.17 Si.sub.3
390
1.5
1600
0.77
2.9 4.4 34,810
88,060
Fe.sub.78.5 Ti.sub.1.5 B.sub.17 Si.sub.3
390
1.5
1600
0.69
6.4 2.5 26,620
49,460
Fe.sub.73 Nb.sub.3 B.sub.20 Si.sub.4
390
1.5
1600
0.70
2.9 3.3 45,850
102,970
Fe.sub.73 V.sub.3 B.sub.20 Si.sub.4
390
1.0
1600
0.81
2.2 3.1 59,211
148,401
Fe.sub.78.5 W.sub.1.5 B.sub.17 Si.sub.3
390
1.0
1600
0.99
3.6 3.1 38,790
106,670
Fe.sub.78.5 Zr.sub.1.5 B.sub.17 Si.sub.3
390
1.0
1600
1.15
3.5 5.3 32,390
106,330
Fe.sub.73 Ta.sub.3 B.sub.20 Si.sub.4
390
1.0
1600
0.80
2.5 3.0 47,850
119,670
__________________________________________________________________________
Example 3
Fe-M-B-Si-C System
Ribbons having compositions given by Fe.sub.100-a-b-c-d M.sub.a -B.sub.b
-Si.sub.c -C.sub.d and having dimensions about 0.5-5 cm wide and about 20
to 50 .mu.m thick were formed as in Example 1.
The magnetic and thermal data are summarized in Table IX below. The
magnetic properties of these glassy alloys after annealing are presented
in Table X.
The line frequency magnetic properties of these metallic glasses are
comparable to those containing molybdenum (Example 1).
A combination of low ac core loss and high impedance permeability at line
frequency is achieved in the metallic glasses of the present invention.
The thermal stability is also shown to be excellent as evidenced by high
crystallization temperature. These improved combination of properties of
the metallic glasses of the present invention renders these compositions
suitable for line frequency magnetic devices such as ground fault
interrupters, current/potential transformers and the like.
TABLE IX
__________________________________________________________________________
Examples of basic physical and magnetic properties
of Fe--M--B--Si--C amorphous alloys where M = Cr or Mo. .theta..sub.f
and T.sub.x1 are the ferromagnetic Curie and first crystalli-
zation temperature, respectively. B.sub.s and .lambda..sub.s are the
room temperature saturation induction and saturation
magnetostriction, respectively.
Composition
Ex. No.
Fe Cr
Mo B Si
C .theta..sub.f (.degree.C.)
B/.sub.r (T)
.lambda..sub.s (10.sup.-6)
T.sub.x1 (.degree.C.)
__________________________________________________________________________
9 76 1.5
1.5
17 4 -- 362 1.39
15.6 535
10 76 3 -- 17 2 2 324 1.36
14.3 511
11 76 --
3 17 2 2 299 1.30
17.3 535
12 77 1.5
-- 16 5 0.5
359 1.48
25.1 523
13 78 --
2 13 6 1 324 1.36
24.4 525
14 78 2 -- 13 6 1 339 1.40
21.4 514
15 78 2 -- 12 7 1 331 1.37
26.3 521
16 78 2 -- 13.5
5.5
1 341 1.41
22.7 509
17 78 --
2 12 7 1 336 1.35
22.6 516
18 76.75
2 -- 16 5 0.25
352 1.46
20.5 534
__________________________________________________________________________
TABLE X
______________________________________
Examples of the 60 Hz magnetic properties of
Fe.sub.100-a-b-c-d M.sub.a B.sub.b Si.sub.c C.sub.d metallic glasses,
where M is one
of molybdenum and chromium, listed in Table IX. Samples
were annealed at temperature T.sub.a for a holding time t.sub.a in
a 1600 A/m longitudinal field. Values of the dc coer-
cive field H.sub.c and remanent induction B.sub.r and 60 Hz impe-
dance permeability .mu..sub.z and core loss L at specified maxi-
mum induction level B.sub.m are given.
L
Example
T.sub.a
t.sub.a
B.sub.r
H.sub.c
(mW/kg .mu..sub.z
Number (.degree.C.)
(h) (T) (A/m) at 0.1 T)
0.1 T 0.5 T
______________________________________
12 400 1 1.19 1.1 2.5 80,470 210,830
13 400 1 0.98 1.4 2.5 74,080 204,710
14 400 1 1.01 2.8 5.0 35,570 116,810
15 390 1.5 1.02 1.7 3.0 61,640 173,740
16 400 1 1.17 2.5 4.9 38,680 129,500
______________________________________
TABLE XI
______________________________________
Magnetic properties of the metallic glass
Fe.sub.76.75 Cr.sub.2 B.sub.16 Si.sub.5 C.sub.0.25 heat-treated at
temperature T.sub.a for
a holding time t.sub.a in the presence of various longitu-
dinal magnetic fields. Toroids were cooled to room tem-
perature at a rate -3.degree. C./min. following the heat-treat-
ment. Core loss (L) and impedance permeability (.mu..sub.z)
were measured using sinusoidal field excitation at 60 Hz
to a maximum induction B.sub.m as indicated.
______________________________________
Example T.sub.a t.sub.a Annealing H.sub.c
B.sub.r
Number (.degree.C.)
(h) Field (A/m)
(A/m) (T)
______________________________________
1 400 1 800 0.87 1.26
2 420 1 800 1.3 1.19
3 380 1 800 1.2 1.13
4 400 1 2,400 -- --
5 400 0.25 800 -- --
6 400 2 800 -- --
7 400 1 4,000 0.58 1.29
8 400 1 200 0.73 1.25
______________________________________
L (mW/kg,
.mu..sub.z
Example B.sub.m = 0.1 T)
0.1 T 0.4 T 0.6 T
______________________________________
1 1.4 143,080 259,220
293,850
2 2.9 73,250 182,550
227,110
3 2.0 92,990 212,500
259,330
4 1.6 127,180 221,070
--
5 2.5 86,860 -- --
6 2.0 93,830 -- --
7 3.2 64,550 -- --
8 1.5 133,400 268,560
--
______________________________________
The magnetic properties of these glassy alloys after annealing in a
longitudinal applied field are presented in Table X. Various annealing
conditions for the metallic glass Fe.sub.76.75 Cr.sub.2 B.sub.16 Si.sub.5
C.sub.0.25 and the obtained results are summarized in Table XI. Frequency
dependence of permeability of this optimally annealed alloy is listed in
Table XII.
Table XIII lists magnetic properties of the metallic glass alloy
Fe.sub.76.75 Cr.sub.2 B.sub.16 Si.sub.5 C.sub.0.25 heated to 400.degree.
C., held for 1 h, and cooled below 200.degree. C. at various rates, all in
the presence of a 1600 A/m longitudinal field. Values of dc remanent
induction (B.sub.r), dc coercive field (H.sub.c) and 60 Hz core loss (L)
and impedance permeability (.mu..sub.z) are shown for a maximum induction
(B.sub.m). The best properties are seen to have resulted from cooling
rates of -0.5.degree. C./min to -10.degree. C./min.
TABLE XIII
______________________________________
L
Average Cooling
B.sub.r
H.sub.c (mW/kg) .mu..sub.z
Rate (.degree.C./min)
(T) (A/m) (Bm = 0.1 T)
0.1 T 0.5 T
______________________________________
-1 1.29 0.73 1.5 138,250
285,480
-3 1.26 0.87 1.4 143,080
276,535
-10 1.26 0.73 1.4 141,880
288,920
-1000* 0.59 2.8 1.7 95,810
223,570
______________________________________
*Quenched in water
The presence of chromium or molybdenum is seen to increase the permeability
and the crystallization temperature and to lower the ac core loss,
exciting power and magnetostriction. Especially noted is the fact that the
optimally heat-treated metallic glass Fe.sub.76.75 Cr.sub.2 B.sub.16
Si.sub.5 C.sub.0.25 of the present invention has a coercivity of 0.5 A/m
and has a low core loss of 1.4 mW/kg and impedance permeability of 300,000
at 60 Hz and at the induction level of 0.6 Tesla. The combination of these
properties make these compositions suitable for line frequency devices
such as ground fault interrupters and current transformers.
TABLE XII
______________________________________
Frequency dependence of impedance permeability .mu..sub.z
of metallic glass Fe.sub.76.75 Cr.sub.2 B.sub.16 Si.sub.5 C.sub.0.25
annealed for 1 h
at 400.degree. C. with an 800 A/m longitudinal field.
f (H.sub.z) 0.1 (T) 0.6 (T)
______________________________________
50 182,290 459,370
100 151,080 319,430
200 117,700 207,830
500 72,820 108,500
1000 47,330 62,390
2000 31,00 38,550
______________________________________
TABLE XV
______________________________________
Field dependence of the 60 Hz impedance permeabi-
lity of metallic glass Fe.sub.76.75 Cr.sub.2 B.sub.16 Si.sub.5 Co.sub..25
annealed for
1 h at 400.degree. C. with transverse and longitudinal fields of
8000 and 1600 A/m, respectively, showing peak applied 60
Hz magnetic field H.sub.m, impedance permeability .mu..sub.z, and
maximum induction B.sub.m.
H.sub.m (A/m) .mu..sub.z
B.sub.m (Tesla)
______________________________________
0.226 19,080 0.005
0.394 45,030 0.002
0.566 66,070 0.047
1.131 107,670 0.135
2.263 129,710 0.369
3.394 126,670 0.540
4.525 117,890 0.670
5.657 109,490 0.778
6.788 102,230 0.872
______________________________________
Table XIV shows magnetic properties of the metallic glass Fe.sub.76.75
Cr.sub.2 B.sub.16 Si.sub.5 C.sub.0.25 annealed in the presence of various
transverse magnetic fields. Table XV shows the detailed field dependence
of impedance permeability of optimally transversely annealed Fe.sub.76.75
Cr.sub.2 B.sub.16 Si.sub.5 C.sub.0.25. That permeability is at least
40,000, and varies by no more than a factor of three for applied fields
ranging from 0.4 to 10.0 A/m. The resulting material is especially suited
for line frequency current/potential transformers in which the
near-constant permeability renders the output nearly linearly over a wide
range of applied fields.
TABLE XIV
______________________________________
Magnetic properties of the metallic glass
Fe.sub.76.75 Cr.sub.2 B.sub.16 Si.sub.5 C.sub.0.25 heat-treated at
temperature T.sub.a for
a holding time t.sub.a in the presence of various transverse
(H.perp.) and, optionally, longitudinal (H.parallel.) magnetic
fields. Toroids were cooled to room temperature at
about -3.degree. C./min. following the heat treatment. Coer-
civity (H.sub.c) and remanent induction (B.sub.r) were measured
from dc BH loops. Core loss (L) and impedance perme-
ability (.mu..sub.z) were measured using sinusoidal field
excitation at 60 Hz to a maximum induction B.sub.m as
indicated.
______________________________________
Example
T.sub.a
t.sub.a
Annealing Field
H.sub.c
B.sub.r
Number (.degree.C.)
(h) H.parallel. (A/m)
H.perp. (A/m)
(A/m) (T)
______________________________________
16 425 2 1,600 8,000 3.2 0.56
17 415 2 1,600 8,000 1.7 0.31
18 400 2 1,600 8,000 1.3 0.23
19 385 2 1,600 8,000 1.4 0.31
20 400 1 800 16,000 1.0 0.30
21 400 1 240 8,000 1.1 0.36
22 400 1 1,600 8,000 0.87 0.20
23 400 1 800 8,000 1.0 0.21
24 400 1 800 4,000 0.87 0.30
25 400 1 0 4,000 1.0 0.85
26 400 1 0 2,400 1.0 0.93
27 400 1 0 800 0.80 1.04
28 400 1 0 8,000 1.3 0.53
29 400 1 800 800 0.58 0.51
30 400 1 2,400 8,000 1.5 0.23
31 400 1 0 16,000 -- --
______________________________________
Example L (mW/kg) .mu..sub.z
Number (B.sub.m = 0.1 T)
0.1 T 0.4 T 0.6 T
______________________________________
16 4.3 34,850 73,600
79,080
17 2.7 50,060 87,780
87,210
18 1.9 63,570 97,920
127,380
19 1.4 69,390 97,170
93,070
20 1.5 62,600 76,490
68,170
21 1.4 152,220 100,910
89,728
22 1.2 97,850 135,540
129,925
23 1.3 74,870 101,700
100,510
24 1.2 115,815 178,640
188,420
25 1.8 98,590 191,300
211,120
26 1.6 115,260 242,370
278,340
27 1.8 82,680 124,630
102,490
28 1.4 141,530 267,840
305,870
29 1.4 122,690 215,880
236,660
30 1.5 61,190 73,870
--
31 2.1 70,274 92,080
--
______________________________________
Having thus described the invention in rather full detail, it will be
understood that this detail need not be strictly adhered to but that
various changes and modifications may suggest themselves to one skilled in
the art, all falling within the scope of the present invention as defined
by the subjoined claims.
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